By way of example, this type of device is found in the field of aeronautics and more precisely in a joystick that is used for piloting aircraft, aeroplanes or helicopters. The pilot manoeuvres this joystick in order to modify the trim of his aircraft. It is essential to have precise knowledge of the position of the joystick in order to reflect the orders from the pilot. The joystick is commonly arranged between the legs of the pilot and has several degrees of freedom, thus allowing the pilot to control several types of mobile elements on his aircraft, such as the ailerons and the elevator. By way of example, the joystick may be mobile on the basis of two rotations or one rotation and one translation. There have recently appeared scaled-down joysticks called minijoysticks, which still allow the pilot to control his aircraft.
The invention is concerned with converting the movements of the joystick into electrical information. More precisely, for each degree of freedom, the joystick has at least one potentiometer allowing the position of the joystick to be converted into electrical information in the form of a DC voltage. The potentiometer may be rotary in order to convert a rotation of the joystick or may be linear in order to convert a translation of a joystick or of a minijoystick.
The invention is not limited to a joystick allowing an aircraft to be piloted. The invention can be implemented for any use of a potentiometer.
It is known practice to apply a DC voltage between the two ends of the potentiometer and to read the voltage that is present on the slider of the potentiometer in order to obtain the sought information. This reading is performed at high impedance in order to avoid losses of linearity between the position of the slider and the voltage that is read. This high impedance results in a very small current which does not allow good continuity to be guaranteed of the contacts. Faults may occur at the level of the contact of the slider in the potentiometer itself or at the level of contacts outside the potentiometer, for example in a connector linking said potentiometer to the environment thereof. The use of gilded contacts allows the quality of the connections to be improved but does not provide a perfect solution to the problems pertaining to the continuity of the contacts.
Moreover, fault detection may be difficult to implement. A continuity fault may become apparent only when the slider is moved, which may be critical to the task of an aircraft. The pilot would thus notice a fault in his joystick only when he wished to manoeuvre his aircraft.